Use Kirchoff Current Law to determine the unknown currents

I am really confused on how to simplify the circuit.

Circuit:
http://imageshack.us/photo/my-images/43/screenshot20130225at102.png/

IR1 = 20mA - (5 + 7)mA = 8mA
IR2 = IR1 + 7mA = 8mA + 7mA = 15mA
I neg = I total = IR2 + 5mA = 15mA + 5mA = 20mA